Canine Vector-Borne Diseases of Working Dogs of the Sri Lanka Air Force, Free-Roaming, and Privately-Owned Dogs

Abstract

Background Canine vector-borne diseases (CVBDs) are a significant health problem among dogs globally. The veterinary records show that the military working dogs of Sri Lanka die early at an average age of six years and CVBDs have been listed as one of the speculated causes. This study examined CVBDs in the working dogs of the Sri Lanka Air Force (SLAF) together with free-roaming and privately-owned dogs living close to the SLAF establishments and country-wide. Methods Blood samples were collected from the cephalic vein for a three year period, from July 2016 to July 2019. Giemsa stained thin blood smears were observed under light microscopy. Results A total of 668 dogs were sampled, of which 169 were infected (25.3%) with hemoparasites. The prevalence of infections among the SLAF working dogs (22.5%), free-roaming (26.3%), or privately-owned (26.2%) dogs did not differ significantly (Chi-square test, p > 0.05). A large number of infected dogs were asymptomatic (57.4%), which was significantly higher in free-roaming dogs (96.3%) compared to the SLAF (41.1%) and privately-owned dogs (38.2%; p < 0.0001) but not between SLAF dogs and privately-owned dogs (χ2 = 0.005, p > 0.938). Seven hemoparasites were identified: Babesia gibsoni, B. canis, Ehrlichia canis, Anaplasma platys, Leishmania sp., Hepatozoon canis, and microfilariae. The most common infection was B. gibsoni (13.8%) followed by E. canis (9.9%) and A. platys (4.3%). There was no difference in the prevalence of B. gibsoni in the three categories of dogs (χ2 = 2.61, p = 0.10). Leishmania and H. canis were always presented as single infections, while microfilaria as mixed infections. Conclusions Even though the SLAF dogs are thoroughly quarantined before introducing them to the military units, the infection prevalence was similar compared to other dog categories. They have likely acquired the infections through ticks and other arthropod vectors. This is the first comprehensive and comparative island-wide study of dog CVBDs of Sri Lanka, especially the military dogs at the SLAF. It highlights that most infected dogs, especially the free-roaming ones, did not show clinical signs. Although it is speculated that they may act as reservoirs of infection, asymptomatic dogs' ability to spread these CVBDS should be investigated.

Development of a Highly Sensitive Nested PCR and Its Application for the Diagnosis of Cutaneous Leishmaniasis in Sri Lanka

“…Studies aiming to find animal reservoirs found 2 out of 151 dogs (1.32%) positive for Leishmania amastigotes [ 5 ], rK39 positivity in 1 out of 114 dogs (0.87%) [ 6 ], and in 4 out of 51 (7.8%) dogs in another study [ 7 ]. A more recent survey among 668 dogs in 18 out of 25 districts in Sri Lanka revealed a Leishmania amastigote prevalence of only 0.9% (2/668) in blood [ 9 ]. These findings suggest the possibility of dogs acting as reservoir hosts [ 10 , 11 ].…”